Why is Shmuelparticularly Unhappy when he shows up at the fence being absent for two days?

Shmuel is particularly unhappy when he shows up at the fence after being absent for two days because he is worried about his father, who has gone missing. His concern reflects the fear and uncertainty faced by those in the concentration camp, highlighting the personal loss and trauma experienced by individuals in such dire circumstances. Additionally, his absence underscores the isolation and helplessness he feels in a situation where families are being torn apart.